Not Quite Dead...
Captain Picard has never actually died throughout The Next Generation, at least not permanently. He has, however, endured near-death experiences. In his youth, he was arrogant and cocky, and this reckless behaviour almost cost him his life when he taunted a group of Nausicaan thugs on Starbase Earhart, shortly after he had graduated from Starfleet Academy. During this incident, young Jean-Luc was stabbed through the back with a Nausicaan shortsword, which had pierced his heart. Picard only survived due to being so close to a hospital at the time and he recieved an artificial vascular implant to replace his damaged heart. This event was one of the most enlightening moments of Picard's life and led to a significant personality change in his later years, resulting in the sophisticated, upstanding and respected officer that commands the Federation flagship.
In TNG's sixth season episode "Tapestry", Captain Picard and several of his staff were attacked during a diplomatic conference. Picard was fatally wounded and died in his ship's sickbay, but rather than pass on, he found himself in a white void along with his long-time rival, the godlike entity called Q. Q revealed that Picard had perished and explained the circumstances, pointing out that the captain's artificial heart had failed. He then offered Picard the opportunity to change his fate by taking him back in time to his youth, specifically the incident at Starbase Earhart when he first got his artificial heart. Ensured that only his own personal timeline and peace of mind were at stake, Picard went about trying to alter his fate so that he would never recieve the injury to his heart. While he did prevent his injury, Picard also alienated his friends who were present during the incident. His Starfleet career was also dramatically changed: while he still served on the Enterprise in the altered future, he served as a lowly Ensign. Q explained that Picard never decided to take any risks during his career in this alternate timeline, that he always "played it safe". As a result, he never befriended his would-be crewmates and remained an Ensign even during his middle-age years. Disgusted by the turn his life had taken, Picard pleaded to Q to return everything to the way it was, preferring to die in the present with a full, satisying life behind him than as the dreary, unremarkable man of this alternate time. Q granted Picard his wish and then took him back to the moment when he got stabbed at Earhart. Moments after being stabbed, Picard woke up in the present on a biobed, surrounded by his friends and colleagues, and he laughed as he awoke, just as he had laughed when he was stabbed back then.